Process for the preparation of phenylhydrazines

ABSTRACT

A process for the preparation of a phenylhydrazine or an inorganic acid salt thereof of the formula (1): 
                 
 
wherein X is a hydrogen or halogen atom; Y is a halogen atom; and W is a hydrogen atom or —ZR in which Z is an oxygen or sulfur atom, and R is a hydrogen atom, an alkyl group, a haloalkyl group, and so on, by the hydrolysis of a phenylhydrazine derivative of the formula (2): 
                 
 
where X, Y and W are the same as defined above, and the Q groups are a hydrogen atom, an ammonium group or an alkali metal atom in the presence of water and an inorganic acid, in which the concentration of the inorganic acid is at least 6 moles per 1 kg of water in a reaction system.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a process for the preparation of aphenylhydrazine or an inorganic acid salt thereof of the formula (1):

wherein X is a hydrogen atom or a halogen atom; Y is a halogen atom; andW is a hydrogen atom or —ZR in which Z is an oxygen atom or a sulfuratom, and R is a hydrogen atom, a C₁-C₆ alkyl group, a C₁-C₆ haloalkylgroup, a C₃-C₈ cycloalkyl group, a benzyl group, a C₃-C₆ alkenyl group,a C₃-C₆ haloalkenyl group, a C₃-C₆ alkynyl group, a cyano-C₁-C₆ alkylgroup, a C₂-C₈ alkoxyalkyl group, a C₂-C₈ alkylthioalkyl group, acarboxy-C₁-C₆ alkyl group, (C₁-C₈ alkoxy) carbonyl-C₁-C₆ alkyl group, a[(C₁-C₄ alkoxy)-C₁-C₄ alkoxy]carbonyl-C₁-C₆ alkyl group, (C₃-C₈cycloalkoxy)carbonyl -C₁-C₆ alkyl group or a [(C₁-C₆alkoxy)carbonyl-C₁-C₆ alkyl]oxycarbonyl-C₁-C₆ alkyl group.

A phenylhydrazine of the formula (1) is a useful intermediate for thepreparation of, for example, pyridazin-3-on compounds of the formulae(4):

which have good herbicidal activities.

2. Prior Art

JP-A-9-323977 describes that a phenylhydrazine of the above formula (1)is synthesized by diazotizing an aniline derivative of the formula (3):

wherein X, Y and W are the same as defined above, and then reducing thediazotized compound with tin chloride.

However, the above synthesis process has drawbacks such that a reactionmixture has low filterability when insoluble tin-containing by-productsare removed by filtration after the reaction, since the reduction isperformed with tin chloride, and that tin compounds should be treatedafter the reaction. Therefore, such a synthesis process may not beindustrially preferred. Thus, it is highly desired to develop a newsynthesis process of a phenylhydrazine or an inorganic acid salt thereofof the formula (1) using no metal reducing agents.

SUMMARY OF THE INVENTION

Extensive studies have been made to solve the drawbacks of theconventional synthesis process. As a result, it has been found that aphenylhydrazine or an inorganic acid salt thereof of the formula (1) isadvantageously obtained by hydrolyzing a phenylhydrazine derivative ofthe following formula (2) by allowing the phenylhydrazine derivative incontact with an inorganic acid in a concentration of at least 6 moles ofthe inorganic acid per 1 kg of water in a reaction system, andfurthermore dehalogenated by-products can be efficiently reduced.

Accordingly, the present invention provides a process for thepreparation of a phenylhydrazine or an inorganic acid salt thereof ofthe formula (1):

wherein X is a hydrogen atom or a halogen atom; Y is a halogen atom; andW is a hydrogen atom or —ZR in which Z is an oxygen atom or a sulfuratom, and R is a hydrogen atom, a C₁-C₆ alkyl group, a C₁-C₆ haloalkylgroup, a C₃-C₆ cycloalkyl group, a benzyl group, a C₃-C₆ alkenyl group,a C₃-C₆ haloalkenyl group, a C₃-C₆ alkynyl group, a cyano-C₁-C₆ alkylgroup, a C₂-C₈ alkoxyalkyl group, a C₂-C₈ alkylthioalkyl group, acarboxy-C₁-C₆ alkyl group, (C₁-C₈ alkoxy)carbonyl-C₁-C₆, alkyl group, a[(C₁-C₄ alkoxy)-C₁-C₄ alkoxy]carbonyl-C₁-C₆ alkyl group, (C₃-C₈cycloalkoxy)carbonyl-C₁-C₆ alkyl group or a [(C₁-C₆ alkoxy)carbonyl-C₁-C₆ alkyl]oxycarbonyl-C₁-C₆ alkyl group comprising the stepof hydrolyzing a phenylhydrazine derivative of the formula (2):

wherein X, Y and W are the same as defined above, and the Q groups arethe same or different and represent a hydrogen atom, an ammonium groupor an alkali metal atom in the presence of water and an inorganic acid,wherein the concentration of the inorganic acid is at least 6 moles per1 kg of water in a reaction system.

DETAILED DESCRIPTION OF THE INVENTION

Herein, a halogen atom for X and Y may be a fluorine atom, a chlorineatom, a bromine atom or an iodine atom.

Examples of a C₁-C₆ alkyl group for R include a methyl group, an ethylgroup, an isopropyl group, a propyl group, an isobutyl group, atert.-butyl group, an amyl group, an isoamyl group, a tert.-amyl group,etc.

Examples of a C₁-C₆ haloalkyl group include a 2,2,2-trifluoroethylgroup, etc.

Examples of a C₃-C₈ cycloalkyl group include a cyclopropyl group, acyclobutyl group, a cyclopentyl group, a cyclohexyl group, etc.

Examples of a C₃-C₆ alkenyl group include an allyl group, a1-methyl-2-propenyl group, a 3-butenyl group, a 2-butenyl group, a3-methyl-2-butenyl group, a 2-methyl-3-butenyl group, etc.

Examples of a C₃-C₆ haloalkenyl group include a 2-chloro-2-propenylgroup, a 3,3-dichloro-2-propenyl group, etc.

Examples of a C₃-C₆ alkynyl group include a propargyl group, a1-methyl-2-propynyl group, a 2-butynyl group, a 1,1-dimethyl-2-propynylgroup, etc.

Examples of a cyano-C₁-C₆ alkyl group preferably include a C₁-C₆cyanoalkyl group such as a cyanomethyl group, etc.

Examples of a C₂-C₈ alkoxyalkyl group include a methoxyethyl group, anethoxymethyl group, an ethoxyethyl group, etc.

Examples of a C₂-C₈ alkylthioalkyl group include a methylthioethylgroup, etc.

Examples of a carboxy-C₁-C₆ alkyl group include a carboxymethyl group, a1-carboxyethyl group, a 2-carboxyethyl group, etc.

Examples of (C₁-C₆ alkoxy) carbonyl-C₁-C₆ alkyl group include amethoxycarbonylmethyl group, an ethoxycarbonylmethyl group, apropoxycarbonylmethyl group, an isopropoxycarbonylmethyl group, abutoxycarbonylmethyl group, an isobutoxycarbonylmethyl group, atert.-butoxycarbonylmethyl group, an amyloxycarbonylmethyl group, anisoamyloxycarbonylmethyl group, a tert.-amyloxy-carbonylmethyl group, a1-methoxycarbonylethyl group, a 1-ethoxycarbonylethyl group, a1-propoxycarbonylethyl group, a 1-isopropoxycarbonylethyl group, a1-butoxycarbonylethyl group, a 1-isobutoxycarbonylethyl group, a1-tert.-butoxycarbonylethyl group, a 1-amyloxycarbonylethyl group, a1-isomyloxycarbony-ethyl group, a 1-tert.-amyloxycarbonylethyl group,etc.

Examples of a [(C₁-C₆ alkoxy)-C₁-C₆ alkoxy]carbonyl-C₁-C₆ alkyl groupinclude a methoxyethoxycarbonylmethyl group, a1-methoxyethoxycarbonylethyl group, etc.

Examples of (C₃-C₈ cycloalkoxy)carbonyl-C₁-C₆ alkyl group include acyclobutyloxycarbonylmethyl group, a cyclopentyloxycarbonylmethyl group,a cyclohexyloxycarbonyl-methyl group, a 1-cyclobutyloxycarbonylethylgroup, a 1-cyclopentyloxycarbonylethyl group, a1-cyclohexyloxy-carbonylethyl group, etc.

Examples of a [(C₁-C₆ alkoxy)carbonyl-C₁-C₆ alkyl]oxy-carbonyl-C₁-C₆alkyl group include an (ethoxycarbonyl)methoxy-carbonylmethyl group,etc.

Examples of an alkali metal atom for Q include a sodium atom, apotassium atom, etc.

A phenylhydrazine derivative of the formula (2) may be prepared bydiazotizing an aniline derivative of the formula (3) and then reactingthe obtained diazonium salt with sulfurous acid, a sulfite salt or ahydrogensulfite salt.

A diazotizing agent used in the above preparation method is usually anitrite salt. Examples of a nitrite salt include sodium nitrite,potassium nitrite, etc. A nitrite salt is usually used in the form of anaqueous solution, although a nitrite salt in a solid form may be used.The amount of a nitrite salt is usually from 1 to 1.2 moles per one moleof an aniline derivative of the formula (3).

In general, an inorganic acid is used in the diazotizing reaction.Examples of an inorganic acid include hydrochloric acid, sulfuric acid,phosphoric acid, nitric acid, etc. Preferably, hydrochloric acid andsulfuric acid are used. Usually, an inorganic acid is used in the formof an aqueous solution.

The amount of an inorganic acid is about 1 to 10 moles, preferably about2 to 6 moles, more preferably about 2.5 to 4 moles, per one mole of ananiline derivative of the formula (3).

In the diazotizing reaction, the order of the addition of reagents isnot limited. Usually, an aniline derivative is mixed with the aqueoussolution of an inorganic acid, and then the aqueous solution of anitrite salt is added thereto.

A reaction temperature is usually from about −20 to 20° C., preferablyfrom about −10 to 100, more preferably from about −5 to 5° C.

Examples of a sulfite salt used as a reducing agent include ammoniumsulfite, sodium sulfite, potassium sulfite, etc. Examples of ahydrogensulfite salt include ammonium hydrogensulfite, sodiumhydrogensulfite, potassium hydrogensulfite, etc. They are usually usedin the form of an aqueous solution, although they may be used in a solidform.

The amount of sulfurous acid, a sulfite salt or a hydrogensulfite saltis usually at least 2 moles, preferably from about 2.5 to 4 moles, perone mole of an aniline derivative of the formula (3).

pH of the reaction system is adjusted usually in the range between 5.5and 8, preferably in the range between 6 and 7.5. The pH of the reactionsystem can be adjusted with acids (e.g. hydrochloric acid, sulfuricacid, etc.), or aqueous solutions of alkali compounds (e.g. sodiumhydroxide, potassium hydroxide, ammonia, etc.).

In the above reaction, a diazonium salt, which has been obtained bydiazotizing an aniline derivative of the formula (3), is added to anaqueous solution containing sulfurous acid, a sulfite or ahydrogensulfite, pH of which is adjusted in the range between 5.5 and 8.A reaction temperature is usually from about 0 to 80° C., preferablyfrom about 10 to 70° C.

A reaction time varies with other conditions such as kinds and amountsof reagents, a reaction temperature, and the like, and cannot beunconditionally limited. The reaction time is usually from about 30minutes to about 24 hours.

After the termination of the reaction, the obtained reaction mixture isfiltrated, and thus a hydrophobic phenylhydrazine derivative of theformula (2) is recovered. A water-soluble phenylhydrazine derivative ofthe formula (2) can be recovered by concentration, or extraction with anorganic solvent followed by concentration. Furthermore, the recoveredphenylhydrazine derivative can be purified by recrystallization, etc.

The phenylhydrazine derivative of the formula (2) formed in theabove-described reaction may be used in the hydrolysis reaction in thepresence of an inorganic acid, as it is, in the form of an aqueoussolution without being isolated.

Aniline derivatives of the formula (3) are known from, for example,EP-A-61741, U.S. Pat. Nos. 4,670,046, 4,770,695, 4,709,409, 4,640,707,4,720,927 and 5,169,431, JP-A-63-156787, and the like, or may beprepared by the methods described in these patent publications.

Typical examples of a phenylhydrazine derivative of the formula (2) arelisted in Table 1.

TABLE 1 (2)

Compound No. X Y W Q 2-1 H Cl H Na 2-2 F Cl H Na 2-3 F Cl OH Na 2-4 F ClOH NH₄ 2-5 F Cl OCH(CH₃)₂ Na 2-6 F Cl OCH₂C≡CH Na 2-7 F Cl OCH₂COOH Na2-8 F Cl SCH₂C≡CH Na 2-9 F Cl SCH₂COOH Na  2-10 Cl Cl H Na  2-11 Cl ClOCH(CH₃)₂ Na  2-12 F Cl OCH₃ Na  2-13 F Cl OCH₂CH₃ Na

In the present invention, a phenylhydrazine of the formula (1) can beobtained by hydrolyzing a phenylhydrazine derivative of the formula (2).

The hydrolysis is performed using an inorganic acid. An inorganic acidis preferably a protonic acid such as hydrochloric acid or sulfuricacid. Furthermore, the aqueous solution of an inorganic acid may beused.

An organic solvent may be used together with an inorganic acid, insofaras the organic solvent does not interfere with the hydrolysis.

The amount of an inorganic acid is usually at least 1 mole, preferablyfrom 4 to 50 moles, per one mole of a phenylhydrazine derivative of theformula (2).

The concentration of an inorganic acid is preferably at least 6 molesper 1 kg of water in the reaction system, from the viewpoint of a yield.The concentration of an inorganic acid in the reaction system ispreferably set within the prescribed range by taking into account theamount of the inorganic acid and that of water contained in an aqueoussolution of the acid and in the phenylhydrazine derivative of theformula (2) or an aqueous solution thereof. The aqueous solution of thephenylhydrazine derivative of the formula (2) may be prepared bydilution with water or by the steps of a diazotization process andsubsequent reduction as described above in which various aqueoussolutions of reactants as mentioned and water are used.

In the process of the present invention, a phenylhydrazine derivative ofthe formula (2) or its aqueous solution (or suspension) is added to aninorganic acid or its aqueous solution, although an inorganic acid orits aqueous solution may be added to a phenylhydrazine derivative of theformula (2) or its aqueous solution (or suspension).

Alternatively, the aqueous solution of a phenylhydrazine derivative ofthe formula (2) is concentrated and then reacted with an inorganic acid.

A reaction temperature in the hydrolysis is usually from −5 to 80° C.,preferably from 0 to 50° C.

A reaction time for the hydrolysis varies with other conditions such askinds and amounts of reagents, a reaction temperature, and the like, andcannot be unconditionally limited. The hydrolysis reaction time isusually from about 30 minutes to about 24 hours.

After the termination of the hydrolysis, the obtained reaction mixtureis filtered as it is, or neutralized with an alkaline aqueous solutionof, for example, sodium hydroxide, and then filtrated. Thus, aphenylhydrazine or an inorganic acid salt thereof of the formula (1) isrecovered. The recovered phenylhydrazine or an inorganic acid saltthereof can be purified by recrystallization, etc.

Typical examples of a phenylhydrazine of the formula (1) are listed inTable 2, but the present invention is not limited to those exemplifiedcompounds.

TABLE 2 (1)

Compound No. X Y W 1-1 H Cl H 1-2 F Cl H 1-3 F Cl OCH(CH₃)₂ 1-4 F Cl OH1-5 F Cl OCH₂C≡CH 1-6 F Cl OCH₂COOH 1-7 F Cl SCH₂C≡CH 1-8 F Cl SCH₂COOH1-9 Cl Cl H  1-10 Cl Cl OCH(CH₃)₂  1-11 F Cl OCH₃  1-12 F Cl OCH₂CH₃

EFFECTS OF THE INVENTION

According to the present invention, a phenylhydrazine of the formula (1)can be efficiently prepared by hydrolyzing a phenylhydrazine derivativeof the formula (2) in the presence of water without the use of any tincompound and without the isolation of the phenylhydrazine derivativefrom a reaction mixture.

The present invention will be illustrated by following Examples, whichdo not limit the scope of the present invention in any way.

EXAMPLE 1

4-Chloro-2-fluoro-5-hydroxyaniline (162.0 g; content: 99.6%, 0.999 mole)was added to 10% hydrochloric acid (1093.3 g) at 25° C. while stirring.Then, a 35% aqueous solution of sodium nitrite (205.9 g) was dropwiseadded to the mixture at a temperature of −3° C. to 0° C. over 1 hour todiazotize 4-chloro-2-fluoro-5-hydroxyaniline to obtain an aqueoussolution of a corresponding diazonium salt (1456.7 g).

The diazonium salt was quickly added at 10° C. to an aqueous solution ofsodium sulfite, which had been prepared by adding sodium sulfite (398.1g) to water (1323.2 g) and then adjusting pH of the mixture at 7.2 with95% sulfuric acid (15.1 g), and the mixture was heated up to 65° C., andmaintained at the same temperature for 2 hours. Thus, the aqueoussolution (3141.5 g) of sodium4-chloro-2-fluoro-5-hydroxyphenylhydrazine-N,N′-disulfonate wasobtained. According to LC-IS analysis, the yield of this sodium salt was96.0% based on 4-chloro-2-fluoro-5-hydroxyaniline.

The obtained aqueous solution of disodium4-chloro-2-fluoro-5-hydroxyphenylhydrazine-N,N′-disulfonate was dropwiseadded to 35% hydrochloric acid (2913.8 g, 27.97 moles), whichcorresponds to 28 moles per one mole of4-chloro-2-fluoro-5-hydroxyaniline, over 2.5 hours while coolinghydrochloric acid at 10° C., and further reacted at the same temperaturefor 8 hours to obtain a reaction mixture (6048.7 g) (90.0% of4-chloro-2-fluoro-5-hydroxyphenylhydrazine; 3.1% of the dechlorinatedcompound (by-product); LC area percentages). After the filtration of thereaction mixture, the residue was dried to obtain a pale pink solidmixture containing 4-chloro-2-fluoro-5-hydroxyphenylhydrazinehydrochloride (438.7 g) (95.6% of4-chloro-2-fluoro-5-hydroxyphenylhydrazine; 0.3% of the dechlorinatedcompound (by-product); LC area percentages).

According to LC-IS analysis, the yield of4-chloro-2-fluoro-5-hydroxyphenylhydrazine was 89.3% based on4-chloro-2-fluoro-5-hydroxyaniline.

The water content in the reaction system means the total amount of watercontained in 10% hydrochloric acid, water contained in the 35% aqueoussolution of sodium nitrite, water added to sodium sulfite, watercontained in 95% sulfuric acid, and water contained in 35% hydrochloricacid, and it was 4336 g. Thus, the amount of the inorganic acids in thereaction system was 6.5 moles per 1 kg of water.

EXAMPLE 2-1

An aqueous solution (1314.1 g) of disodium4-chloro-2-fluoro-5-hydroxyphenylhydrazine-N,N′-disulfonate was preparedin the same manner as in Example 1 using 10% hydrochloric acid (437.7g), 4-chloro-2-fluoro-5-hydroxyaniline (65.0 g; content: 99.6 g; 0.401mole), a 35% aqueous solution of sodium nitrite (83.1 g), water (539.6g), sodium sulfite (159.5 g) and 95% sulfuric acid (12.7 g). Theobtained aqueous solution was concentrated to 865.9 g by evaporatingwater at 56° C. under 107 mmHg over 4 hours.

EXAMPLE 2-2

Then, the concentrated aqueous solution (266.4 g) of disodium4-chloro-2-fluoro-5-hydroxyphenylhydrazine-N,N′-disulfonate was dropwiseadded to 35% hydrochloric acid (223.5 g, 2.146 moles) over 2.5 hourswhile cooling hydrochloric acid at 10° C., and further reacted at thesame temperature for 9 hours to obtain a reaction mixture (486.5 g)(81.2% of 4-chloro-2-fluoro-5-hydroxyphenylhydrazine; 2.7% of thedechlorinated compound (by-product); LC area percentages). After thefiltration of the reaction mixture, the residue was dried to obtain apale pink solid mixture containing4-chloro-2-fluoro-5-hydroxyphenylhydrazine hydrochloride (61.9 g) (96.5%of 4-chloro-2-fluoro-5-hydroxyphenylhydrazine; 0.1% of the dechlorinatedcompound (by-product); LC area percentages).

According to LC-IS analysis, the yield of4-chloro-2-fluoro-5-hydroxyphenylhydrazine was 89.4% based on4-chloro-2-fluoro-5-hydroxyaniline.

The water contained in the reaction mixture was 311 g, and thus theamount of the inorganic acids in the reaction system was 6.9 moles per 1kg of water.

EXAMPLE 3

4-Chloro-2-fluoro-5-hydroxyaniline (20.1 g; content: 99.6%; 0.124 mole)was added to 10% hydrochloric acid (135.8 g) at 25° C. while stirring.Then, a 35% aqueous solution of sodium nitrite (25.9 g) was dropwiseadded to the mixture at a temperature of −3° C. to 0° C. over 1 hour todiazotize 4-chloro-2-fluoro-5-hydroxyaniline to obtain an aqueoussolution of a corresponding diazonium salt (181.7 g).

The diazonium salt was quickly added at 10° C. to a 50% aqueous solutionof ammonium hydrogensulfite (73.8 g), pH of which had been adjusted at7.2 by adding a 30% aqueous solution of sodium hydroxide (41.0 g), andthe mixture was heated up to 65° C., and maintained at the sametemperature for 2 hours. Thus, the aqueous solution (290.5 g) ofdiammonium 4-chloro-2-fluoro-5-hydroxyphenylhydrazine-N,N′-disulfonatewas obtained.

The obtained aqueous solution of diammonium4-chloro-2-fluoro-5-hydroxyphenylhydrazine-N,N′-disulfonate was dropwiseadded to 35% hydrochloric acid (361.5 g, 3.470 moles) over 2 hours whilecooling hydrochloric acid at 10° C., and further reacted at the sametemperature for 4 hours to obtain a reaction mixture (648.4 g) (93.5% of4-chloro-2-fluoro-5-hydroxyphenylhydrazine; 0.6% of the dechlorinatedcompound (by-product); LC area percentages). After the filtration of thereaction mixture, the residue was dried to obtain a pale pink solidmixture containing 4-chloro-2-fluoro-5-hydroxyphenylhydrazinehydrochloride (44.4 g) (96.5% of4-chloro-2-fluoro-5-hydroxyphenylhydrazine; no dechlorinated compoundbeing detected; LC area percentages).

According to LC-IS analysis, the yield of4-chloro-2-fluoro-5-hydroxyphenylhydrazine was 88.0% based on4-chloro-C₁₋₂-fluoro-5-hydroxyaniline.

The water contained in the reaction mixture was 440 g, and thus theamount of the inorganic acids in the reaction system was 7.9 moles per 1kg of water.

EXAMPLE 4

The aqueous solution of disodium4-chloro-2-fluoro-5-hydroxyphenylhydrazine-N,N′-disulfonate (2610.6 g)was prepared in the same manner as in Example 1 except that 10%hydrochloric acid (896.4 g), 4-chloro-2-fluoro-5-hydroxyaniline (132.9g, content: 99.6%, 0.819 mole), a 35% aqueous solution of sodium nitrite(169.6 g), water (1084.5 g), sodium sulfite (326.2 g) and 96% sulfuricacid (14.8 g) were used.

The obtained aqueous solution (200.0 g) of disodium4-chloro-2-fluoro-5-hydroxyphenylhydrazine-N,N′-disulfonate was cooledto 10° C. Then, to the cooled solution, 96% sulfuric acid (178.5 g,1.747 moles) was charged at 10° C. over 30 minutes, and reacted at 15°C. for 2 hours to obtain a reaction mixture (377.9 g) (90.4% of4-chloro-2-fluoro-5-hydroxyphenylhydrazine; 1.2% of the dechlorinatedcompound (by-product); LC area percentages). After the filtration of thereaction mixture, the residue was washed with saturated brine (115.7 g)and dried to obtain an ash gray solid mixture containing4-chloro-2-fluoro-5-hydroxyphenylhydrazine sulfate. (21.2 g) (96.2% of4-chloro-2-fluoro-5-hydroxyphenylhydrazine; 0.3% of the dechlorinatedcompound (by-product); LC area percentages).

According to LC-IS analysis, the yield of4-chloro-2-fluoro-5-hydroxyphenylhydrazine was 85.5% based on 4-chloro-2-fluoro-5-hydroxyaniline.

The water contained in the reaction mixture was 161 g, and thus theamount of the inorganic acids in the reaction system was 10.9 moles per1 kg of water.

The results of Examples 1-4 are summarized in Table 3.

TABLE 3 Amount of Inorganic acid per 1 kg of Yield¹⁾ of water inreaction phenyl- Inorganic system hydrazines acid (moles) (%) Example 1Hydrochloric acid 6.5 89.3 Example 2 Hydrochloric acid 6.9 89.4 Example3 Hydrochloric acid 7.9 88.0 Example 4 Sulfuric acid 10.9 85.5 Note: ¹⁾Ayield based on the raw material aniline derivative.

1. A process for the preparation of a phenylhydrazine or an inorganicacid salt thereof of the formula (1):

wherein X is a hydrogen atom or a halogen atom; Y is a halogen atom; andW is a hydrogen atom or —ZR in which Z is an oxygen atom or a sulfuratom, and R is a hydrogen atom, a C₁-C₆ alkyl group, a C₁-C₆ haloalkylgroup, a C₃-C₆ cycloalkyl group, a benzyl group, a C₃-C₆ alkenyl group,a C₃-C₆ haloalkenyl group, a C₃-C₆ alkynyl group, a cyano-C₁-C₆ alkylgroup, a C₂-C₈ alkoxyalkyl group, a C₂-C₈ alkylthioalkyl group, acarboxy-C₁-C₆ alkyl group, (C₁-C₈ alkoxy) carbonyl-C₁-C₆ alkyl group, a[(C₁-C₄ alkoxy)-C₁-C₄ alkoxy]carbonyl-C₁-C₆ alkyl group, (C₃-C₈cycloalkoxy) carbonyl-C₁-C₆ alkyl group or a [(C₁-C₆alkoxy)carbonyl-C₁-C₆ alkyl]oxycarbonyl-C₁-C₆ alkyl group; said methodconsisting essentially of the step of hydrolyzing a phenylhydrazinederivative of the formula (2):

in the presence of water and an inorganic acid, wherein theconcentration of the inorganic acid is at least 6 moles per 1 kg ofwater in a reaction system; wherein X, Y and W of formula (2) are thesame as defined in formula (1), and the Q groups are the same ordifferent from each other and represent a hydrogen atom, an ammoniumgroup or an alkali metal atom.
 2. The process according to claim 1,wherein said phenylhydrazine derivative of the formula (2) is preparedby diazotizing an aniline derivative of the formula (3):

and then reacting the obtained diazonium salt with at least one compoundselected from the group consisting of sulfurous acid, sulfite salts andhydrogensulfite salts.
 3. The process according to claim 1, wherein aphenylhydrazine or an inorganic acid salt thereof of the formula (1) isfiltrated after hydrolysis.
 4. The process according to claim 1, whereinthe amount of said inorganic acid is from 4 to 50 moles per one mole ofsaid phenylhydrazine derivative of the formula (2).
 5. The processaccording to claim 1, wherein X is a halogen atom.
 6. The processaccording to claim 5, wherein W is —ZR.